The present invention relates generally to dust and vapor seals and, more particularly, to a flexible seal for a duct passing through a wall.
The present invention was developed to meet a need in the aircraft industry for an effective seal assembly for sealing the gap around a hot air duct where the duct passes through a wall, such as a bulkhead or firewall.
More particularly, large commercial transport airplanes typically include an air duct network through which hot air, known as bleed air, is conducted from the airplane engines to various other parts of the airplane. The bleed air is drawn from the compressor stages of the turbine engines and conducted through the duct network at temperatures of up to 957.degree. F. and pressures of up to 312 psi. The pressurized bleed air is used for cabin pressurization and wing and inlet anti-icing.
The bleed air is distributed to the various parts of the airplane through steel ducts approximately five inches in diameter. The ducts pass through an engine firewall as well as various bulkheads and similar wall members. At each point where the duct passes through a wall there is a need for a seal assembly that provides a tight seal between the wall and the duct and yet permits the duct to undergo some movement relative to the wall in response to normal structural flexing of the airplane and thermal expansion and contraction of the duct. There is also a need for a seal that will accommodate misalignment of the duct with respect to the seal bulkhead location due to manufacturing tolerance accumulation. Where the duct passes through walls separating pressurized from unpressurized cabin spaces it is further desirable that the seal be capable of containing moderate positive pressure on the order of fifteen pounds per square inch. Additionally, at the point where the duct passes through the engine firewall there is a need for a seal assembly that provides a barrier against penetration of liquid fuel as well as fuel vapors, and which also allows the duct to undergo axial, lateral, and bending motions relative to the wall.
Accordingly, it is the primary object and purpose of the present invention to provide a seal assembly for a duct passing through a wall. More specifically, it is the object and purpose of the present invention to provide such a seal assembly that allows the duct to move relative to the wall and yet which also provides a fluid-tight barrier between the duct and the wall.
It is another object of the present invention to provide a seal assembly that obtains the foregoing objects and purposes and which is particularly adapted to accommodate a hot bleed air duct in an airplane.
It is another more specific object of the invention to provide a seal assembly for an air duct passing through an opening in a wall member wherein the duct is free to undergo relative axial motion through the opening, as well as relative lateral motion within the opening and angular or rotational motion about the opening.
It is also an object of the invention to obtain the foregoing objects with a seal assembly that occupies a minimum of space, which is readily serviceable and which permits ready installation and removal of the duct without necessitating removal of the seal assembly.